Brain pathway makes head and face pain very draining

(Reuters Health) - If head and facial pain seem stronger and scarier than pain elsewhere, it’s because a special pathway in the brain is heightening our emotions from pain at those sites, according to studies in mice.

People usually experience head and facial pain as more severe and emotionally draining than body pain, but the biological basis of this remains something of a mystery.

It turns out that pain signals in the face travel to a different place in the brain than pain stimuli in other parts of the body, researchers say.

Dr. Fan Wang from Duke University Medical Center in Durham, North Carolina and colleagues looked at the brain circuitry involved in pain perception in mice, focusing on differences between responses to painful stimuli to the face and to the paw.

They knew already that pain signals from the face travel to both sides of a brain area called the lateral parabrachial nucleus, or PBL. The new study showed that signals traveled from there to multiple centers in the brain related to emotions and instincts.

As it turns out, the brain cells in the PBL also get input from these emotion centers, the researchers explain in Nature Neuroscience.

In contrast, pain signals from the paw travel through the spinal cord and end up in a different part of the parabrachial nucleus on the side of the brain opposite the side of the paw that was stimulated.

“Pain, especially chronic pain, is not just a sensory disorder, but also an emotional disorder, and chronic head and face pain directly and robustly affect the patient’s emotional suffering,” Wang told Reuters Health by email. “Therefore, it is important to treat the emotional suffering of chronic pain patients.”

Dr. Arne May from Universitaetsklinikum Hamburg Eppendorf in Germany, who has researched facial pain extensively, told Reuters Health by email, ”Most will be surprised that, indeed, facial pain is perceived as more threatening than (the same) pain of the arm or leg. This work starts to unravel the physiological background.”

“Why this seemingly explicit pathway exists” is still unclear, he said. “Probably because the face/head is more important to the system in terms of survival.”